KOSI BAY, SOUTH AFRICA: Necklace of fish traps

Do you see a rabbit or a duck??

Devil’s Pitchfork

The circles appear to rotate when you move your head closer and further away from the screen while looking at the dot in the center. Our peripheral vision interprets the relative increase or decrease of the image in the retina as rotational motion of the slanted lines.

The shade of the center dot is the same in all the squares. The shade of the background influences how we perceive it. All squares are uniformly shaded, but each square seems

lighter on its left edge than on its right edge.

Apparent movement of the streams is created by afterimagesas our eyes shift to examine the picture.

Which lines are longer?

Which one seems larger??

Which one is larger?

Which circle is larger?